Moving picture coding method, and moving picture decoding method

Abstract

According to the present invention, a moving picture coding apparatus (70) for performing inter-picture predictive coding for pictures constituting a moving picture is provided with a coding unit (103) for performing predictive error coding for image data; a decoding unit (105) for performing predictive error decoding for an output from the coding unit (103); a reference picture memory (117) for holding output data from the decoding unit (105); and a motion vector detection unit (108) for detecting motion vectors on the basis of the decoded image data stored in the memory. When coding a B picture as a target picture, information indicating whether or not the target picture should be used as a reference picture when coding another picture is added as header information. Therefore, in a decoding apparatus for decoding a bit stream Bs outputted from the moving picture coding apparatus (70), management of a memory for holding the reference picture can be facilitated on the basis of the header information.

Description

TECHNICAL FIELD [0001] The present invention relates to a moving picture coding method and a moving picture decoding method and, more particularly, to a method for coding or decoding pictures constituting a moving picture with reference to other pictures of the moving picture. BACKGROUND ART [0002] Generally, in coding of pictures constituting a moving picture, each picture is divided into plural blocks, and compressive coding (hereinafter, also referred to simply as “coding”) of image information possessed by each picture is carried out for every block, utilizing redundancies in the space direction and time direction of the moving picture. As a coding process utilizing redundancy in the space direction, there is intra-picture coding utilizing correlation of pixel values in a picture. As a coding process utilizing redundancy in the time direction, there is inter-picture predictive coding utilizing correlation of pixel values between pictures. The inter-picture predictive coding is a...

AI Technical Summary

Benefits of technology

[0073] According to the present invention, in the above-described moving picture coding method, the picture position information is expressed with a shorter length code as the distance on the display time axis from the target picture to the already-coded B picture that is referred to in coding the target picture is shorter.

[0151] Further, in the present invention, there is provided a moving picture decoding method for decoding each of plural pictures constituting a moving picture to convert a bit stream corresponding to each picture into image data, which method includes a decoding step of decoding a target picture to be decoded with reference to an already-decoded picture, wherein a flag indicating whether or not the target picture should be used as a candidate for a reference picture when decoding another picture that follows the target picture, is described in the bit stream, and in the decoding step, management of the decoded target picture is carried out on the basis of the flag. Therefore, it is possible to correctly decode a bit stream corresponding to a B picture, which is generated by using, as forward reference pictures, a B picture subjected to bidirectional predictive coding as well as a P picture subjected to forward predictive coding.

Problems solved by technology

In this case, however, the reference index [1] assigned to the P picture P16 that is closer to the target picture (B picture B15) on the display time axis X becomes larger than the reference index [0] assigned to the P picture P19 that is far from the B picture B15, resulting in degradation of coding efficiency.

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